Cardiovascular Journal of Africa: Vol 26 No 4 (July/August 2015)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 4, July/August 2015

AFRICA

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addition, hsTnI level was the only independent predictor of AF

recurrence in multivariate analysis.

The STOP-AF trial is the only randomised study that

compared treatment efficacy of cryo-balloon ablation versus anti-

arrhythmic drugs for paroxysmal AF. After 12 months, nearly

70% of the patients treated with the cryo-balloon remained free

from AF, compared to only 7.3% on drug therapy.

The success

rate of treatment was higher with CA than with standard RF

ablation.

Aytemir

et al

studied the predictors of AF recurrence in

patients who underwent cryo-balloon ablation for paroxysmal

AF. In this study, freedom from AF after a single ablation

procedure was 68.53 and 90.83% in patients undergoing PVI with

first- and second-generation cryo-balloon catheters, respectively.

Left atrial diameter, early AF recurrence and second-generation

cryo-balloon catheter use were independent predictors for late

AF recurrence.

In our study, we used second-generation cryo-balloon

catheters in all cases and 88% of patients were free of AF

recurrence. In patients with AF recurrence, the LA diameter was

larger and the duration of AF was longer. After multivariate

analysis, these two parameters were not found to be independent

predictors of recurrence.

The role of troponin release after CA of PVs for paroxysmal

AF in predicting ablation outcome is not clear. Cardiac

biomarkers have been used to estimate myocardial lesion size

after ablation procedures with different energy sources. Del

Rey

et al

demonstrated that RF ablation increased troponin

levels in almost all patients, whereas other cardiac biomarkers

remained within health-related reference limits. It has also been

shown that increase in biomarker levels and the amount of

myocardial damage after RF catheter ablation depend on the

number of RF pulses and the site of ablation.

Increase in myocardial injury biomarker levels after CA was

first described by Oswald

et al

In patients with atrial flutter, CA

showed significantly higher troponin levels following ablation

compared to RF ablation, with declining levels the following day.

They observed equal findings for CK and CK-MB levels, both

significantly higher in the CA group.

Comparison of troponin increases after ablation procedures

for AF with RF or cryo-energy is controversial. Kühne

et al

compared troponin release in patients undergoing CA and RF

ablation. In their study, post-procedural troponin levels were

higher in the RF ablation group. The study by Siklody

et al

revealed no significant differences in myocardial injury markers

between patients treated with CA or RF ablation. In the same

field, Schmidt

et al

compared RF ablation and CA for their

impact on markers for myocardial injury. They demonstrated

that CA causes significantly higher troponin release compared

to RF ablation.

In our study, CA resulted in a larger troponin increase

compared to previous studies using RF ablation.

12,23,24

To the best

of our knowledge, our study is the first that shows the prognostic

role of hsTnI levels in patients undergoing CA for paroxysmal

AF. Our study revealed that lower post-procedural hsTnI level is

an independent predictor of AF recurrence.

Although we also analysed other myocardial injury markers,

we found only hsTnI level to be a predictor of AF recurrence.

This may be related to the better sensitivity of hsTnI to show

myocardial damage than any other markers of injury.

Bordignon

et al

compared myocardial biomarker release

using first- and second-generation cryo-balloons. They revealed

that cumulative freezing time was related to biomarker release.

In our study, there was no correlation between biomarker release

and procedural data.

Single-procedure success rates of PVI by RF ablation in

patients with paroxysmal AF remain unsatisfactory. Although

PVI is the main target in paroxysmal AF, substrate abnormality

in the PV antrum may play a critical role in the AF mechanism.

Additional ablation of the PV antrum after PVI may increase the

efficacy of the procedure.

Higher troponin release with CA may

be linked to larger ablation damage in the LA compared to the

RF-based PVI procedure. This finding may explain the potential

advantage of CA beyond PV isolation.

Preliminary results of our unpublished data on patients with

long-standing persistent AF showed that CA of the PVs resulted

in a significant decrease in the CFE area.

This contributary

role may be predominantly on the posterior wall of the LA due

to its vicinity.

Limitations

Our study has several limitations. A major limitation is the

relatively small sample size. Another limitation is the poor

relationship between biomarker measurement and lesion region,

and we did not find a casual relationship. The mode of follow

up, which was performed only by 24-hour Holter monitoring or

occasional event-driven ECG is a further limitation, and clinical

judgment may be questionable. The increase in hsTn levels after

ablation was not region specific and it may not indicate ablation

of the critical site maintaining the arrhythmia.

Although two patients underwent redo EPS to define the

exact electrophysiological cause of recurrence, EPS evaluation

was unfortunately not performed on all patients with recurrence.

Therefore we could not conclude whether all recurrence was

associated with inadequate substrate ablation in patients with

lower post-CA hsTn levels.

Although patients in whom AF persisted at the end of CA

underwent CFE mapping, the localisation of CFE may not

predict the exact focus of triggers in patients with paroxysmal

AF. Given the difficulty in precisely locating and ablating these

triggers, an alternative approach that simply seeks to electrically

isolate the PV from the LA seems logical.

Evaluation of histopathological data would be the gold

standard to assess the extent and localisation of ablation

lesions. However, the requirement for animal or

in vitro

studies

constitutes the pivotal problem in this evaluation. Cardiac

magnetic resonance imaging after using a cryo-balloon in

patients with/or without recurrence may contribute to providing

distinct information with regard to cryo-thermal cardiac lesions

and associations between biomarker release, and should be a

field for future research.

Conclusion

Despite these limitations, the results of this study indicate that

lower post-procedural hsTn level was associated with higher

recurrence rates and may be linked to inadequate atrial ablation

by cryo-balloon catheter.